Fig. 5: Performance of water electrolysis using QAPPT/BN composite HEM.

a Ionic conductivity and thermal conductivity of QAPPT and QAPPT/8.9%BN HEMs. The inset shows the chemical structure of QAPPT. b Polarization curves measured in 15% KOH at 90 °C and 110 °C. c Transient in-situ stability test based on transiently oscillated current densities between 1 A cm^–2 and 0.1 A cm^–2, holding for 2 s and standing for 1 s for each current density every cycle. d Resistance changes of the electrolyzer before and after the transient stability test. e In-situ stability test in 15% KOH at a constant current density of 1 A cm⁻². The inset shows the polarization curves of the pristine HEM and the HEM after the in-situ stability test at 90 °C. f Comparison of voltage degradation rate and temperature between the proposed QAPPT/BN composite HEM and reported HEMs^{11,20,21,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60}. Testing parameters, including current density and KOH concentration are indicated by bubble size and color contrast, respectively. Lifetime is placed beside the bubbles. The samples in this work are indicated by the blue shadow. g Comparison of ex-situ stability and in-situ stability of the QAPPT/BN composite HEM and reported HEMs in HEMWE^{11,20,21,36,41,42,43,45,48,49,52,53,57,58,59,60}. The reported HEMs are indicated by the blue shadow.